102 



liilion Foi' roducinr; Iho <to1(1 chloride wns 1 volume formic 

 acid to !t Nolumes waler. In this solulioii Ihe eulliire only 

 remained lor 21 hours and was Ihen i-eady for mounting. 

 This modification gave just as good staining results and 

 was much safer. In most cases the central portion of the 

 culture is lost, hut this is of little consequence hecause no 

 details can he ohserved in that paiM of Ihe cidture; it ap- 

 pears always as an opacjue hlack mass. 



Lew^is and Lewis often fix (heir special cultiu'es in 

 Zenker's solution witliout the acetic acid, sometimes they 

 add a little osmic acid just before using it. The Zenker's 

 solution is composed of: potassium bichromate 2 per cent, 

 sodium sulphate 1 per cent, corrosive sublimate 5 per cent. 



Quite usually Lewis's cultures nre fixed with iodine 

 vapor by i)lacing a small flake of |)ure iodine in Ihe bottom 

 of the hollowground slide. The iodine vapor rapidly tints 

 the cells yellowish brown. 



